pointer event madness. file selector crash. <option> crash. rem bugs. insane RAM usage. crash from RAM usage. crash from greedy CSS selectors. canplay event never fired on media.
That's just from the last few weeks. Can't imagine anyone who has built a moderately sized web app would think Safari's biggest problem is just being a little slow on the uptake.
In better news, wkwebview is a big improvement. Hopefully it's a sign of things to come.